page_title: Field cancerization
section_title: Pattern of alterations in a field defect
hierarchical_section_title: Field cancerization / Pattern of alterations in a field defect
caption_attribution_description: English: A colon cancer resection, 22 cm long, had 6 tissue samples evaluated for expression of 3 DNA repair proteins, KU86, ERCC1 and PMS2. All 3 proteins are expressed at near 100% in colon tissue from a person without any colonic neoplasia, but adjacent to a colon cancer, in this instance, there is a field of more than 20 cm in which ERCC1 and PMS2 have reduced expression.
context_page_description: Field cancerization is a biological process in which large areas of cells at a tissue surface or within an organ are affected by carcinogenic alterations. The process arises from exposure to an injurious environment, often over a lengthy period.
context_section_description: The field defect adjacent to a colon cancer consists of the inner surface of the colon (the epithelium) that has about 1 million crypts (indentations in the surface of the epithelium). Each crypt has about 5,000 cells in the shape of a test-tube and all 5,000 cells of the crypt are generated from the few stem cells at the base of the crypt. The stem cells at the base of the crypt can undergo "crypt conversion" where a stem cell with a selective advantage takes over the stem cell niche, and all cells of that crypt display consistent expression (high or low) of a protein being evaluated.
  The diagram shows results obtained by Facista et al. A particular colon resection from a colon cancer patient was evaluated for expression of 3 different DNA repair enzymes: Ku86 (active in the non-homologous end joining pathway), ERCC1 (active in the nucleotide excision DNA repair pathway) and PMS2 (active in the mismatch DNA repair pathway). The percent of crypts in 6 tissue samples taken within the field defect were evaluated for frequency of high levels of expression of each of the repair proteins. Almost every crypt in all tissue samples from this patient showed high expression of KU86. However, the majority of crypts in all 6 tissue samples were reduced or absent in protein expression of ERCC1 and PMS2. The crypts with reduced or absent expression of ERCC1 or PMS2 usually occurred in large patches of adjacent crypts. Both ERCC1 and PMS2, in these tissue samples, were thought to be deficient due to epigenetic alterations.
caption: A colon cancer resection, 22 cm long, had 6 tissue samples evaluated for expression of 3 DNA repair proteins, Ku86, ERCC1 and PMS2. All 3 proteins are expressed at near 100% in colon tissue from a person without any colonic neoplasia, but adjacent to a colon cancer, in this instance, there is a field of more than 20 cm in which ERCC1 and PMS2 have reduced expression.
exif: {}